This setting is available in E20: https://docs.mattermost.com/administration/config-settings.html#enable-notification-contents.
An error occurred while saving the commentMichael D. commented
This feature is a basic need for every Mattermost platform and from my perspective MANDATORY to be compliant with GDPR.
You either have to forbid users to write about any personal data in their mattermost messages or you have to
* disable the email notification completely
* or be able to disable to sent out message contents
* or be able to encrypt the emails.
So, at the moment, all Mattermost team instances in the EU violate GDPR in the standard configuration. You can not disable to sent out message contents. You just can disable email notifications completly, but then your users will see a "Preview mode" warning.
As I understand there is a feature in the Enterprise version to disable contents. I propose to move this basic feature in all Mattermost versions and disable to sent out contents by default
Thank you for nominating the feature! Ready-only channels feature is now available in Mattermost v5.22.0 in Enterprise Edition E20 (Beta).